In U.S. application Ser. No. 10/625,198, fully incorporated herein by reference in its entirety, a method is described that is related to the recovery of nitrogen from ammonia that is produced from anaerobic digestion of waste. In the prior process, atmospheric air at ambient temperature is used as the stripping gas. However, if ambient air is used, especially during winter, the temperature of the digested liquid waste can be significantly reduced to a temperature, such as 40° F. to 50° F., that will lower the amount of ammonia and hydrogen sulfide that is stripped from the digested liquid waste. The lower temperature will also negatively affect the efficiency of the biofilter that fixes the nitrogen into a solid form.
Accordingly, there is a need to improve on the prior method to more efficiently recover ammonia, and subsequently nitrogen. The present invention overcomes the drawbacks of the prior method and has further related advantages.